TiO2-HfN Radial Nano-Heterojunction: A Hot Carrier Photoanode for Sunlight-Driven Water-Splitting
Sheng Zeng, Triratna Muneshwar, Saralyn Riddell, Ajay P. Manuel, Ehsan Vahidzadeh, Ryan Kisslinger, Pawan Kumar, Kazi M. Alam, Alexander E. Kobryn, Sergey Gusarov, Ken Cadien, Karthik Shankar
Abstract
The lack of active, stable, earth-abundant, and visible-light absorbing materials to replace plasmonic noble metals is a critical obstacle for researchers in developing highly efficient and cost-effective photocatalytic systems. Herein, a core–shell nanotube catalyst was fabricated consisting of atomic layer deposited HfN shell and anodic TiO2 support layer with full-visible regime photoactivity for photoelectrochemical water splitting. The HfN active layer has two unique characteristics: (1) A large bandgap between optical and acoustic phonon modes and (2) No electronic bandgap, which allows a large population of long life-time hot carriers, which are used to enhance the photoelectrochemical performance. The photocurrent density (≈2.5 mA·cm−2 at 1 V vs. Ag/AgCl) obtained in this study under AM 1.5G 1 Sun illumination is unprecedented, as it is superior to most existing plasmonic noble metal-decorated catalysts and surprisingly indicates a photocurrent response that extends to 730 nm. The result demonstrates the far-reaching application potential of replacing active HER/HOR noble metals such as Au, Ag, Pt, Pd, etc. with low-cost plasmonic ceramics.